The present invention relates to a seat belt retractor reel and more particularly to a seat belt retractor reel suitable for use in a vehicle such as a motor car.
Many different seat belt arrangements have been provided for use in vehicles such as motor cars. A typical seat belt arrangement incorporates a retractor reel adapted to retract the seat belt when the belt is not in use. A typical retractor reel is provided with a mechanism adapted to lock the shaft of the reel when an accident arises. Such a mechanism may include a sensor which is responsive to acceleration or deceleration of the vehicle in such a way that if an acceleration or deceleration in excess of a predetermined limit is detected the sensor responds to cause the shaft of the reel to be locked. Typically such a sensor may comprise a pendulum, or a ball in a cup, or a member adapted to topple over when subjected to a predetermined force. When the pendulum, ball or toppling member move in a predetermined way the locking mechanism is actuated. Additionally various prior art reels also include a sensor responsive to the withdrawal of the belt from the reel, the sensor being adapted to respond to seat belt withdrawal in excess of a predetermined velocity or in excess of a predetermined speed, the sensor being adapted to lock the shaft of the reel if the belt is withdrawn at an excessive speed or with an excessive acceleration. Typically such a sensor incorporates an inertia weight loosely mounted on the shaft and spring biassed to follow movement of the shaft. On rapid movement of the shaft the inertia weight is unable to follow the movement of the shaft, and thus a relative movement occurs between the inertia weight and the shaft. The locking mechanism operates in response to this relative movement.
It has been proposed recently to provide automatic seat belt systems. In such an automatic seat belt system when a person enters a motor vehicle and sits in the seat, the seat belt is automatically located in position retaining the person in the seat. Typically such an automatic seat belt system incorporates a track that is built into the motor vehicle, and one or more carriages are provided which move along the track. The or each carriage carries part of the seat belt. Typically, when a person sits in the seat the carriages move along the track, withdrawing seat belt from a retractor reel, and the carriages move in such a way that the seat belt is located correctly on the person sitting in the vehicle seat, the seat belt then being clamped or retained in position.
If a retractor reel of the type described above is utilised with an automatic seat belt system, as described, various problems can arise.
In a typical prior art retractor reel the sensor that is responsive to vehicle acceleration or deceleration is also responsive to an inclination of the vehicle, since typically the sensor comprises a pendulum, or a ball in a cup, or an element which topples over when subjected to appropriate forces. It will thus be appreciated that if a prior art reel of this type is utilised with an automatic seat belt system as described, if a motor vehicle is parked on a slope when a person enters the motor vehicle, there is a risk that the retractor reel will be in the locked condition, and then when the carriage or carriages move along the track the belt will not be withdrawn from the reel. This is clearly a major problem.
A further problem can arise if a conventional prior art reel is utilised with an automatic seat belt system as described since if the carriage withdraws the belt from the reel with a speed or acceleration which is in excess of the speed or acceleration that causes the sensor responsive to belt movement to react, again the reel will become locked, thus preventing the further withdrawal of belt.
The present invention seeks to provide a seat belt system in which the above-described problem is reduced or obviated.